This invention relates generally to vehicles of the type having convertible sets of wheels, one set being track wheels permitting use of the vehicle on rails and the other set being rubber wheels permitting use of the vehicle on paved or unpaved ground surfaces.
Vehicles of this type are sometimes referred to as rubber-rail cars. Such vehicles are provided with rail bearing track wheels and retractable ground bearing wheels and are commonly used in coal mines and in other industries for supply cars which perform part of their transportation function on rails and part on roads.
In general, when the vehicles are operated on a track, the rubber tired ground wheels are retracted to a position above the rails on each side of the car. At the end of the track, when the track wheels are no longer needed, the ground wheels are lowered and locked in place so that the vehicle can travel over ground. In vehicles of the type currently being used it is necessary to provide ramp-like trenches alongside the rail ties as a transition between the rail and ground operation. As the vehicle is pulled off the end of the track, the ground wheels pick up the weight as the wheels come out of the trenches and lift the track wheels from the rails so that the car can be operated as a trailer. The procedure is reversed when the vehicle is returned to the rails.
Several problems are encountered in using known vehicles of this type. One such problem lies in the difficulty of maintaining the trenches alongside the track. These trenches tend to become filled with debris and dirt and make it very difficult to lower the ground wheels effectively.
Another problem has arisen from the need to move the convertible vehicles during mine clean-up. In most mines battery-powered scoops are used to ensure that the mine floors are kept clean in accordance with Bureau of Mines requirements. These scoops simply push the vehicles aside and, because of the structure of the ground wheel carriages which are invariably cantilever arms mounting each of the four wheels individually, the carriages can become damaged or even destroyed in some instances.
Yet another significant problem encountered with cars of this type lies in the manual handling of the conversion mechanism. The conversion is usually undertaken by a single operator and the lowering of the wheels which are of a substantial weight while at the same time the latching of the carriage is difficult for one person to accomplish alone.
The present convertible vehicle solves these and other problems in a manner not disclosed in the known prior art.